Disk Utility Icon

Options are dimmed in Disk Utility

If some Disk Utility options are dimmed, the choices might not be available for the disk or volume you have selected.

For example, you can only verify or repair permissions for a Mac OS X startup disk, so those choices will be dimmed if you select a disk that isn't a startup disk.

If a disk is write-protected, you cannot verify or repair the disk.

See also

repairing disks